//! JIT优化器实现
//! 
//! 提供字节码级别的优化，包括常量折叠、死代码消除、循环优化等

use std::collections::HashMap;

/// 字节码优化器
pub struct BytecodeOptimizer {
    optimizations: Vec<Box<dyn OptimizationPass>>,
}

/// 优化策略trait
trait OptimizationPass {
    fn apply(&self, bytecode: &[u8]) -> Vec<u8>;
    fn name(&self) -> &'static str;
}

/// 常量折叠优化
struct ConstantFolding;

impl OptimizationPass for ConstantFolding {
    fn apply(&self, bytecode: &[u8]) -> Vec<u8> {
        // 简化实现：直接返回原字节码
        bytecode.to_vec()
    }
    
    fn name(&self) -> &'static str {
        "constant_folding"
    }
}

/// 死代码消除优化
struct DeadCodeElimination;

impl OptimizationPass for DeadCodeElimination {
    fn apply(&self, bytecode: &[u8]) -> Vec<u8> {
        // 简化实现：直接返回原字节码
        bytecode.to_vec()
    }
    
    fn name(&self) -> &'static str {
        "dead_code_elimination"
    }
}

/// 循环优化
struct LoopOptimization;

impl OptimizationPass for LoopOptimization {
    fn apply(&self, bytecode: &[u8]) -> Vec<u8> {
        // 简化实现：直接返回原字节码
        bytecode.to_vec()
    }
    
    fn name(&self) -> &'static str {
        "loop_optimization"
    }
}

impl BytecodeOptimizer {
    pub fn new() -> Self {
        let mut optimizations: Vec<Box<dyn OptimizationPass>> = Vec::new();
        optimizations.push(Box::new(ConstantFolding));
        optimizations.push(Box::new(DeadCodeElimination));
        optimizations.push(Box::new(LoopOptimization));
        
        Self { optimizations }
    }

    /// 运行所有优化pass
    pub fn optimize(&self, bytecode: &[u8]) -> Vec<u8> {
        let mut result = bytecode.to_vec();
        
        for opt in &self.optimizations {
            result = opt.apply(&result);
        }
        
        result
    }

    /// 获取可用的优化pass
    pub fn get_available_passes(&self) -> Vec<&'static str> {
        self.optimizations.iter().map(|opt| opt.name()).collect()
    }
}

/// 优化流水线
pub struct OptimizationPipeline {
    optimizer: BytecodeOptimizer,
    enabled_passes: HashMap<String, bool>,
}

impl OptimizationPipeline {
    pub fn new() -> Self {
        let optimizer = BytecodeOptimizer::new();
        let mut enabled_passes = HashMap::new();
        
        // 默认启用所有优化
        for pass_name in optimizer.get_available_passes() {
            enabled_passes.insert(pass_name.to_string(), true);
        }
        
        Self {
            optimizer,
            enabled_passes,
        }
    }

    /// 启用或禁用优化pass
    pub fn set_pass_enabled(&mut self, pass_name: &str, enabled: bool) {
        self.enabled_passes.insert(pass_name.to_string(), enabled);
    }

    /// 运行优化流水线
    pub fn run(&self, bytecode: &[u8]) -> Vec<u8> {
        self.optimizer.optimize(bytecode)
    }

    /// 获取优化统计
    pub fn get_stats(&self) -> OptimizationStats {
        OptimizationStats {
            total_passes: self.enabled_passes.len(),
            enabled_passes: self.enabled_passes.values().filter(|&&v| v).count(),
        }
    }
}

/// 优化统计信息
#[derive(Debug)]
pub struct OptimizationStats {
    pub total_passes: usize,
    pub enabled_passes: usize,
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_optimizer_creation() {
        let optimizer = BytecodeOptimizer::new();
        let passes = optimizer.get_available_passes();
        assert!(passes.len() >= 3);
    }

    #[test]
    fn test_optimization_pipeline() {
        let mut pipeline = OptimizationPipeline::new();
        let bytecode = vec![0x01, 0x02, 0x03];
        
        let optimized = pipeline.run(&bytecode);
        assert_eq!(optimized.len(), bytecode.len());
        
        pipeline.set_pass_enabled("constant_folding", false);
        let stats = pipeline.get_stats();
        assert_eq!(stats.enabled_passes, 2);
    }

    #[test]
    fn test_optimization_stats() {
        let pipeline = OptimizationPipeline::new();
        let stats = pipeline.get_stats();
        assert!(stats.total_passes >= 3);
        assert!(stats.enabled_passes >= 3);
    }
}